The January transfer window is a notoriously difficult time to improve a squad; clubs are unwilling to let their best players leave midway through the season, and plotting a strategy based on the first half of a campaign can be fraught with problems further down the line.

Nonetheless, gems can still be uncovered in the winter market, with Luis Suarez, Nemanja Vidic, Philippe Coutinho and Patrice Evra among the Premier League legends to be signed during previous January windows.

The most recent edition was not the busiest we have ever seen, but there were still a few notable deals which went through, some of which have proved successful while others are yet to bear fruit.

Here, Sports Mole ranks all 30 players to have joined a Premier League club in January who have made at least one appearance for their new employers.

Often big-money signings do not live up to the hype, particularly in January, and the likes of Fernando Torres to Chelsea and Andy Carroll to Liverpool provided the perfect evidence of that on perhaps the most famous January deadline day ever.

Bruno Fernandes has not fallen into that trap yet, though; the Portuguese playmaker was the subject of the longest-running saga of the window, finally completing his move to Manchester United from Sporting Lisbon on January 29 in a £49.5m switch.

It was the biggest deal of the window, but one which already appears to have had a transformative impact on Ole Gunnar Solskjaer's side.

Fernandes has directly contributed to seven goals in nine games across all competitions, scoring three and creating four, while his performances in his first month at the club earned him the Premier League's February Player of the Month award.

Indeed, Manchester United have fared very well from their January additions so far, with deadline day arrival Odion Ighalo ranking just behind Fernandes as the second-best winter signing.

The Nigerian's arrival was heavily questioned after he joined on loan from Shanghai Shenhua, particularly after United had been linked with a plethora of other striking options before him, but he has quickly quietened those naysayers.

Ighalo has scored four goals in eight appearances across all competitions and, while he is yet to open his account for the club in the Premier League, his performances have been impressive enough to warrant speculation that he could be kept on in a permanent capacity.

The United duo are by far the standout arrivals from January so far, but others have made an impact too. Aston Villa's Mbwana Samatta has already scored twice in his six outings - including a goal in the EFL Cup final and an historic Premier League strike which saw him become the first Tanzanian to net in the competition.

Tottenham Hotspur opened their chequebook to bring in Steven Bergwijn and he enjoyed a dream debut by scoring a fine goal to help Spurs beat Manchester City, while he has since added another goal from his seven Spurs outings.

Gedson Fernandes and Giovani Lo Celso, the latter of whom saw his loan made permanent in January, have had less of an impact since the turn of the year, although certainly not to the extent that Jose Mourinho will be questioning the deals just yet.

Newcastle United and West Ham United have generally fared well in their winter business this year too, with Nabil Bentaleb and Danny Rose quickly settling in the Magpies first team while Jarrod Bowen and Tomas Soucek have made impacts at the London Stadium.

Sheffield United surprised many by spending £27m on Sander Berge, who has made five appearances so far to help the Blades maintain their European push, although their other new recruits - including Jack Rodwell, Jack Robinson and Panagiotis Retsos - have seen much less game time.

The likes of Pepe Reina and Daniel Podence have enjoyed regular minutes without making a noticeable difference to their side's fortunes so far, while Cenk Tosun looked to be a good acquisition from Crystal Palace until he suffered a season-ending injury.

Liverpool's only addition Takumi Minamino has been limited to sub appearances or FA Cup outings so far and is yet to register a single goal or assist, while Newcastle's Valentino Lazaro has had a mixed start to life at the club, scoring once but also being sent off in his opening six Magpies outings.

Danny Drinkwater got off to a torrid start at Aston Villa, being heavily criticised for his role in the 6-1 defeat to Man City on his debut and, while he has featured more regularly than some of those above him our list, his off-field misdemeanours also affect his placing.

Watford spent £7m on Ignacio Pussetto, who is yet to start for the club, but the standout deal in terms of poor value for money so far has been Josh Brownhill to Burnley.

The Clarets brought him in from Bristol City for a £9m fee but he has since been handed just one minute of action, coming on as a late sub in the 3-0 win over Bournemouth.

Sports Mole's full ranking of every January Premier League signing:

1. Bruno Fernandes (£49.5m, Sporting Lisbon - Manchester United)
2. Odion Ighalo (loan, Shanghai Shenhua - Manchester United)
3. Mbwana Samatta (£8.5m, Genk - Aston Villa)
4. Steven Bergwijn (£26.7m, PSV - Tottenham)
5. Nabil Bentaleb (loan, Schalke 04 - Newcastle)
6. Jarrod Bowen (£20m, Hull City - West Ham)
7. Tomas Soucek (loan, Slavia Prague - West Ham)
8. Sander Berge (£27m, Genk - Sheffield United)
9. Danny Rose (loan, Tottenham - Newcastle)
10. Giovani Lo Celso (£27.3m, Real Betis - Tottenham)
11. Gedson Fernandes (loan, Benfica - Tottenham)
12. Ondrej Duda (loan, Hertha Berlin - Norwich)
13. Aaron Mooy (undisclosed, Huddersfield - Brighton)
14. Pepe Reina (loan, AC Milan - Aston Villa)
15. Daniel Podence (£17m, Olympiacos - Wolves)
16. Cenk Tosun (loan, Everton - Crystal Palace)
17. Lukas Rupp (£450,000, Hoffenheim - Norwich)
18. Valentino Lazaro (loan, Inter Milan - Newcastle)
19. Pablo Mari (loan, Flamengo - Arsenal)
20. Takumi Minamino (£7.65m, Red Bull Salzburg - Liverpool)
21. Joao Pedro (undisclosed, Fluminense - Watford)
22. Kyle Walker-Peters (loan, Tottenham - Southampton)
23. Ignacio Pussetto (£7m, Udinese - Watford)
24. Darren Randolph (£4m, Middlesbrough - West Ham)
25. Danny Drinkwater (loan, Chelsea - Aston Villa)
26. Borja Baston (free, Swansea - Aston Villa)
27. Jack Rodwell (free, unattached - Sheffield United)
28. Jack Robinson (£1m, Nottingham Forest - Sheffield United)
29. Panagiotis Retsos (loan, Bayer Leverkusen - Sheffield United)
30. Josh Brownhill (£9m, Bristol City - Burnley)